Impact drill



R. E. SNYDER July 26, 1955 IMPACT DRILL ts-Sheet 2 2 Shee INVENTOR. 205591-15. 5N YDER,

ATTORNEY- I I i T w m .EW 4 Y Original Filed March 15, 1947 United States Patent Q IMPACT DRILL Robert E. Snyder, Pasadena, Calif., assignor to Snyder Oil Tool Corporation, a corporation of California Continuation of application Serial No. 734,989, March 15, 1947. This application February 11, 1952, Serial No. 271,014

16 Claims. (Cl. 255-3) My invention relates generally to impact drills of the type used in earth boring, and more particularly to such drills which are driven by the rotation of a shank or stem within the hole or well being drilled. This application is a cotinuation of my copending application Serial No. 734,989, filed March 15, 1947, and now abandoned.

In my copending applications for Impact Drills, No. 527,179, filed March 20, 1944, now Patent No. 2,425,012, issued August 5, 1947; No. 674,526, filed June 5, 1946 and now abandoned; and No. 714,339 filed December 5,

1946, now Patent No. 2,635,852 issued April 21, 1953, i e

have disclosed new and improved types of rotary impact drills which are operated by the relative rotation between a drill stem and a body rotatably mounted thereon, having blades or vanes to engage the drilling fluid or mud and produce the relative rotation between the stem and the body. Such drills are very satisfactory and have produced results which have heretofore been considered impossible to obtain, but, as is well known in the art, the wide variety of earth formations encountered in drilling wells requires the use of many different types of drills and bits in order to secure the best results. For example, in drilling through various formations which are very hard and brittle, it is desirable to deliver a series of sharp, downwardly directed impacts against the surface being drilled. In other cases, best results are obtained by delivering a very heavy impact, such as might be delivered by a very heavy body moving rather slowly. in the above-mentioned copending applications I have disclosed drills adapted to deliver these types of impacts, but under certain conditions still different types of impacts are desirable in order to obtain the best results. For example, in certain formations it is desirable to have a heavy impact downwardly, followed by a lighter impact in an upward direction to avoid sticking of the bit in the formation being drilled. Some of my previously described drills may be constructed and operated to obtain this result in some degree, but in the device about to be described, this feature has been given a place of greater importance. Furthermore, I have paid particular attention to the design of a resilient mount for the impact member so that the maximum efficiency therefrom may be obtained.

It is therefore a major object of my invention to provide an impact drill which may be operated by the rotation of a drill stem to deliver a heavy impact to an attached bit, these heavy impacts being alternated with lighter imacts. p Another object of my invention is to provide such a drill which, by the choice of a suitable rotational speed of the drill stem, may be caused to deliver both of the above-mentioned impacts to the bit, a single impact to the bit, or no impacts to the bit.

It is a further object of my invention to provide a drill of this type in which the heavy impact is directed downwardly to force the bit into the material being drilled, while the lighter impact is directed upwardly to free the bit from this material to minimize any tendency for the bit to stick in the formation being drilled.

2,713,992 Patented July 26, 1955 Still another object of my invention is to provide a resilient support for the impact body used on a drill of this type, in which a relatively small movement of the operating means is transformed into an enlarged or magnified movement of the impact body.

It is a still further object of my invention to provide a rotary impact drill making use of a resilient suspension which may be operated at its resonant frequency so that the maximum efficiency of the device will be obtained.

These and other objects and advantages of my invention will become apparent from the following description of various embodiments thereof, and from the drawings illustrating those embodiments in which:

Figure 1 is a vertical view, partially in section, of one form of my improved impact drill, with the cam operating means in their lowermost position, immediately after one of the cams has overridden the other;

Figure 2 is asimilar view of the device shown in Figure 1, with the cams about to override each other, and with the impact body raised, preparatory to delivering an impact to the bit;

Figure 3 is a vertical view similar to Figure 1 but of a modified form of my device in which the lighter, intermediate impact is directed upwardly while the major. impact is directed downwardly; v

Figure 4 is a vertical view, partially in cross-section, of another modification of my'device wherein a different resilient suspension of the impact body is provided;

Figure 5 is a view, similar to Figure 4, of another modification in which the cam means is mounted outside of the impact body;

Figure 6 is a vertical view, partially in section, of a drill using a suspension somewhat similar to that shown in Figure 4, and adapted to deliver the type of double impact delivered by the drill shown in Figure 1; and

Figure 7 is a view similar to Figure 6 of still another modification in which the resilient support of Figure 4 is adapted to produce the same type of double impact as that produced by the drill shown in Figure 3.

Referring now to the drawings and particularly to Figures l and 2 thereof, the numeral 10 indicates generally a. shank adapted to be attached to the lower end of a drill stem by any suitable coupling means '(not shown), the coupling being of a typeadapted to transmit rotary motion so that rotation of the drill stem causes a corresponding rotation of the shank. At the lower end of the shank 10 I mount a coupling means 12 adapted to receive'a bit 13, the upper surface of the coupling means preferably being flat to form an anvil 14. An impact producing hammer body, designated generally by the numeral 15, is reciprocably mounted on the shank 10 above the anvil 14, and thus the downward movement of the hammer 15 will cause an impact to be delivered to the bit 13 when the hammer strikes the anvil 14. The construction of the hammer member 15 and the anvil 14 is similar tothat shown and described in my above mentioned copending application Serial No. 674,526 filed June 5, 1946. However, the mounting of the hammer on the shank, the means reciprocating the hammer, and the operation of this presently described device are considerably different from that of the previously mentioned copending application, and the results obtained are likewise different.

To reciprocate the hammer body 15 upon the shank 10, I provide a pair of complementary shaped cams 16 and 17, of which the lower cam 16 is attached to the shank for rotation therewith, while the upper cam 17 is rotatably and reciprocably mounted on the shank to override the lower cam when rotated with respect to the latter. Cams of his general type have been shown and described in my previously mentioned copending applications, and are seen to consist of complementary shaped adjacent cam 'faces having a rise and a fall portion located to produce a lobe so that the upper cam 17 is moved upwardly and then falls to impact against the lower cam 16 as the latter is rotated in a clockwise direction with respect to the upper cam. Since the lower cam 16 is rigidly attached to the shank which is positively driven by the customary drilling equipment (not shown), this cam may be referred to as the driving cam, whereas the upper cam 17 may be considered the driven cam.

Normally, the driven cam 17 tends to rotate with the driving cam 16 because of the friction existing between the engaging faces of the two cams, and consequently some -method of retarding the rotation of the driven cam should be provided if the latter is to reciprocate and impact against the driving cam.

While there are many methods of retarding the rotation of the driven cam 17, I prefer to use the method disclosed in my copending application Serial No. 527,179,

filed March 20, 1944, now Patent No. 2,425,012, wherein a series of blades or vanes engage the drilling fluid or mud within the well, and are connected to the driven cam 17 so that the frictional resistance to the passage of the blades through the fluid tends to retard the rotation of the driven cam sufliciently to cause it to override the driving cam 16.

One very satisfactory form of construction is provided by attaching a series of generally longitudinally extending blades orvanes 20 to the hammer body 15, these blades presenting an appreciable area to the fluid when moved or rotated horizontally, and a much smaller area when moved vertically. The blades 20 may be attached to the body 15 by welding or other suitable means, and the body itself preferably comprises a tubular portion 21 which is maintained substantially coaxial with the shank 10 by an upper collar 22, and by a lower collar 23 which also acts as the hammer surface to impact against the anvil 14. It will be appreciated that all of these members are ruggedly constructed, and are adapted to withstand a considerable amount of abuse such as they will normally receive in the field.

To transmit the retarding force of the body 15 to the driven cam 17, a pair of longitudinally extending slots 24 are formed in the tubular body 21, and a pair of keys 25 are formed on the driven cam 17 to cooperate with the slots so that the cam is free to move axially with respect to the hammer body 15, while rotating at all times therewith.

' If the device thus described is placed in a well having drilling fluid therein and the drill stem is rotated as is customary, the vanes 20 will engage the fluid to retard the rotation of the hammer body 15 with respect to the shank 10. Consequently, the driven cam 17 will likewise be retarded with respect to the driving cam 16 to override and impactagainst the latter. However, the weight of the driven cam 17 is relatively small, and hence only a light impact will be delivered to the bit 13 through the shank 10. However, the hammer body 15 normally has sufficient weight to produce a relatively heavy impact when it hits against the anvil 14, and if the hammer body and the driven cam 17 are rigidly connected together, these impacts will be simultaneous, as has been the case is my previously mentioned copending applications. In order to secure a less rigid construction and a resilient mounting for the hammer body 15, I have provided a suspension system so that the hammer body is not directly connected to driven cam 17 but is resiliently connected thereto so that it may deliver an impact to the bit 13 before or after the impact delivered by the driven cam 17.

As indicated in Figures 1 and 2, the resilient suspension for the hammer body 15 includes a pair of resilient members preferably in the form of helical compression springs and 31 which are connected between the hammer body .15 and the cam means 16 and 17 to transmit the motion of the latter to the hammer body. The helical spring 30 is mounted within the tubular housing 21, surrounding the shank 10, and extends between the upper surface of the driven cam 17 and the lower surface of the upper collar 22. Similarly, the helical spring 31 is located within the tubular body 21 and surrounds the shank 10 between the upper surface of the lower collar 23, and the lower surface of the driving cam 16. Consequently, as the driven cam 17 overrides the driving cam 16, the former is raised and tends to compress the helical spring 30, thereby providing an upwardly directed force on the tubular body 21 which raises the latter, and consequently moves the lower collar 23 upwardly toward the driving cam 16, thereby compressing the helical spring 31. When the driven cam 17 overrides the driving cam 16, the driven cam drops suddenly to the position shown in Figure 1, thereby producing a light downward impact which is transmitted to the bit 13. The springs 30 and 31 which have been compressed to move the body 21 upwardly, are now suddenly released and the body is urged downwardly by both gravity and by compressed spring 31 so that the lower collar 23 impacts against the anvil 14. The spring 30, of course, will be of sufiicient strength to resiliently support the hammer body 15, and to transmit the movement of the cam 17 to the body. Similarly, the spring 31 will be somewhat weaker so that it will not prevent the movement of the hammer body 15, but will nevertheless add materially to the downwardly directed impact delivered by the latter.

It will be noted that the hammer body 15 is resiliently connected to the cam means 16 and 17 and is operated thereby, but because of this resilient suspension, the movement of the hammer body is not limited to the actual lineal movement of the cam means. Consequently, if the driven cam 17 overrides the driving cam 16 at a frequency approximating the resonant frequency of the impact system including the hammer body 15 and the springs 30 and 31, the amplitude of the oscillations of the impact system will tend to increase until very heavy blows are delivered to the anvil 14. Under proper conditions, the movement of the hammer body 15 will materially exceed the movement of the driven cam 17, and hence very powerful blows may be delivered to the anvil 14. It will be noted, however, that the upper end of the helical spring 31 bears against the axially immovable driving cam 16, so that a definite cushioning or bumper effect is obtained which limits the upward travel of the hammer body 15. The work which is done in compressing the springs 30 and 31 is stored in them as potential energy, and is delivered to the hammer body 15 and the drivencam 17 as these latter are moved downwardly.

In the operation of this form of my device, the drill with the bit 13 mounted thereon is lowered into a well, and the customary drilling fluid is forced downwardly through the center of the shank 10 while the shank is rotated in a clockwise direction, as viewed from its upper end, by any convenient means. The drilling fluid then fills the well, and the blades 20 engage the fluid to retard the rotation of the hammer body 15 and thereby cause the driven cam 17 to override the driving cam 16 in the manner just described.

As the driven cam 17 is reciprocated on the shank 10, the helical springs 31 and 31 will be alternately compressed and released, thereby tending to oscillate the hammer body 15. As long as the frequency of oscillation of the driven cam 17 is considerably below the natural frequency of the resilient system, the driven cam will impact against the driving cam 16, and immediately thereafter the lower collar 23 will impact against the anvil 14. After a short period, the driven cam 17 will again impact against the driving cam 16, and the lower shoulder 23 will again impact against the anvil 14. This cycle will be repeated as long as the frequency of oscillation of the driven cam 17 remains the same, but as the frequency is increased, a point is finally reached wherethe frequency of the driven cam 17 is substantially equal to the natural frequency of the resiliently mounted system. At this point, the resonance of the system acts to increase the impact delivered by the hammer body 15 against the anvil 14 by increasing the amplitude of oscillation of the body, thereby providing a longer path for the latter before it impacts against the anvil. Under these conditions, the driven cam 17 will first impact against the driving cam 16, and shortly thereafter the collar 23 of the hammer body 15 will impact against the anvil 14. In this way, there will first be a light but sharp impact caused by the overriding cams 16 and 17, followed by a heavy impact caused by the hammer body 15 hitting the anvil 14. Both of these impacts are directed downwardly, and the lighter impact, caused by the overriding cams, tends to clear the bit 13 and remove any detritus or mud which adheres thereto. Consequently, the principal force of the second or major impact of the hammer body 15 against the anvil 14 is directed against the formation being drilled, and the eificiency of the drill assembly is thereby increased.

Should it be desired to eliminate the heavier or major impact, the rotational speed of the shank It) may be increased to a point where the frequency of reciprocation of the driven cam 17 is considerably above the natural frequency of the resiliently mounted assembly. When this occurs, the driven cam 17 will be moved upwardly by the driving cam 16 as before, and the hammer body 15 will be urged upwardly by reason of the compression of helical spring 30. However, after the lobe of the driven cam 17 has passed the lobe of the driving cam 16 and dropped downwardly, the driven cam is again moved upwardly to a point where it again urges the body 15 upwardly, reaching this point before the hammer body has had suiiicient time to move downwardly and impact against the anvil 14. The hammer body 15 will therefore float at some point near its upper limit of travel without moving downwardly to impact against the anvil 14, and the only impact will be that provided by the overriding of the driven cam 17 and the driving cam 16.

In this way, it is possible to secure three different types of operation from the same drill assembly. For example, if it is desired to operate the drill so that the bit 13 is merely rotated without having any impacts delivered thereto, the shank may be rotated at a relatively low speed so that the frictional resistance developed between the blades Zil and-the drilling fluid is not sufficient to overcome the static friction existing between the rotating shank 10 and the hammer body 15. If the speed is increased, the double impact of the driven cam 17 and the hammer body is obtained, while at still higher speeds only the single impact of the driven cam is secured.

The drill shown in Figures 1 and 2 is designed, as previously mentioned, to provide a relatively light impact followed thereafter by a relatively heavy impact, bothof these impacts being in the samedirection. However, it is sometimes desirable that the light impact be in the opposite direction, or upwardly, while the heavy impact is directed downwardly. Consequently, in Figure 3 I have shown a rotary impact drill of the same general type as that shown in Figures 1 and 2, but with its lighter or cam impact directed upwardly, while the heavier or body impact is directed downwardly.

The drill assembly shown in Figure 3 is very similar to that shown in Figures 1 and 2 and has a shank 16 adapted to be attached to a rotary drill stem (not shown) at its upper end and to have a bit (not shown) attached at its lower end. A coupling member 12 is mounted at the lower end of the shank 10 to receive the bit, and the upper surface of the coupling member is' provided with an anvil 14 against which a hammer body 15 is adapted to impact. The construction of .the hammer member 15 is essentially the same as that of the similarly numbered hammer member of the first described form,

and is provided with fluid engaging vanes mounted S on a tubular body 21 which has an upper collar 22 and a lower collar 23.

To reciprocate the hammer body 15, I provide a driving cam 16a rigidly attached to the shank 10, and a driven cam 17a is mounted on the shank below the driving cam to cooperate with it. The driving cam 16a and the driven cam 17a have complementally-shaped faces having one or more lobes, and the driven cam is mounted for axial and rotational movement with respect to the shank 10. The hammer body 15 is provided with longitudinally extending slots 24 which are adapted to receive keys or splines 25 formed on the driven cam 17a, the slots acting to prevent relative rotation between the hammer body and the driven cam while permitting axial or longitudinal movement of the two.

The hammer body 15 is resiliently supported with respect to the cam members 16a and 17a by helical springs a and 31a of which the spring 30a extends between the upper surface of the driving cam 16a and the lower surface of the upper collar 22, while the spring 31a extends between the lower surface of the driven cam 17a and the upper surface of the collar 23. The springs 30a and 31a are held in compression by the cams 16a and 17a and the collars 22 and 23, and the strength of the springs is such that the hammer body 15 is held with the lower collar 23 an appreciable distance above the anvil 14 when the cams are in the position shown in Figure 3.

However, when the driven cam 17a is rotated with respect to the driving cam 16a, the driven cam is moved downwardly along the shank until the lobes of the cams pass and they return to the position indicated. The downward movement of the driven cam 17a acts to compress the spring 31a and force the hammer body 15 downwardly, thereby increasing the compression of. the spring 30a. When the driven cam 17a overrides the driving cam 16a, the additional force compressing the springs 30a and 31a is removed and the body 15 then moves upwardly. While it is possible to construct the device to operate differently, I prefer to correlate the strength of the springs 30a and 310 with the weight of the hammer body 15 so that the impact face of the lower collar 23 is normally spaced from the upper surface of the anvil 14 a distance slightly greater than that which the driven cam 17a moves downwardly. In this way, if the spring 31a remained rigid as the driven cam 17a moves downwardly, the impact face of the lower collar 23 would not impact against the anvil 14, but

L- instead would be separated a slight distance from it.

However, as the frequency with which the driven cam 17a impacts against the driving cam 16a is increased, the natural frequency of the resilient system is approached. At this natural frequency, the periodic impulses delivered to the resilient system by the overriding cams 16a and 17a will cause the movement of the hammer body 15 to be increased in amplitude until it is impacting heavily against the anvil 14.

It will be noted that the separation between the lower collar 23 and the anvil14 is greater than the lift of the cams 16a and 17a, and consequently the hammer body 15 will not impact against the anvil until the oscillatory speed of the cams approaches the natural frequency of the resilient mounting. However, by decreasing the spacing between the collar 23 and the anvil 14, the lower collar may be caused to bear against the anvil just as the driven cam 17a overrides the driving cam 16a, or may be caused to impact against the anvil slightly before the cams override. In the latter case, however, the spring 31a will be compressed even more as the cams override, thereby materially increasing the frictional resistance between the cam faces, normally an undesirable feature.

In the operation of this form of my drill, the hammer body 15 is retarded with respect to the rotating shank 10, and the driven cam 17a is therefore rotated with respect to the driving cam 16a. As these cams override, the'driven cam 17a will be moved upwardly by the action of springs 30a and 31a to impact against the driving cam 16a, thereby delivering an upwardly directed impact to the shank 10 which is transmitted to the bit. At very low rotational speeds of the shank 10, the resistance of the drilling fluid to the passage of the vanes therethrough is not sulficient to overcome the friction existing between the hammer body 15 and the shank 10, and hence there will be no overriding of the cams 16a and 17a. Above some critical speed which is determined by this friction, by the viscosity of the drilling fluid, and by other related factors, relative rotation between the driven cams 17a and the driving cam 16a will occur. This slow relative rotation of the cams will produce the light, upwardly directed impact previously mentioned, but will not produce any'downwardly directed impact, since the hammer body 15 is not moved a sufficient distance to impact against the anvil 1.4. As the rotational speed of the shank 11 is increased, the cams 16a and 17a override each other at a rate which approaches the natural frequency of the resilient system, and the amplitude of movement of the hammer member 15 is increased until the collar 23 hits against the anvil 14 to deliver an impact to the latter. At this speed, the bit first receives an upwardly directed impact which tends to loosen it from the formation being drilled, shaking off any detritus which may cling to its drilling edges, and shortly thereafter receives a heavy, downwardly directed impact which forces its cutting edges into the formation to aid in the drilling thereof.

As the rotational speed of the shank 10 is still further increased, a point will be reached where the movement of the hammer body 15 is not fast enough to follow the movement of the driven cam 17a, and hence the hammer body will float in a lowered position without impacting against the anvil 14, in which case the drill acts as a high speed jar to withdraw a stuck bit from the formation. Since a'similar but slower result can be obtained by operating the shank 10 at a speed below that sufiicient to produce the double impact, the high speed operation of the shank 10 will normally be seldom used.

It will be realized that the two forms of my drill heretofore described are very similar and differ only in the position and operation of the overriding cam means. In each of these forms, a light impact is delivered to the shank 10 by the impacting of the driven cam 17 or 17a 7 against the driving cam 16 or 1611, and a heavier impact is then delivered by the hammer body 15 against the anvil 14. While both of these drills will operate at lower speeds, their maximum etliciency is achieved when the shank 10 is rotated at a speed which will cause the hammer body 15 to be reciprocated at the natural frequency of the resilient system. In both of these forms, it will be noted that one of the helical springs bears against a longitudinally immovable member so that the resilient system is, in effect, anchored at one end and oscillated at the other end. It is possible, of course, to drive both ends of the resilient system simultaneously, and in Figures 4 to 7 I have indicated various methods of accomplishing this.

While there are various methods of accomplishing this, one of the simplest ways to drive both ends of the resilient system is to connect both of the springs to the driven cam instead of connecting only one of them thereto. Such a system is illustrated in Figure 4, wherein a shank 10 is adapted to be attached to a conventional rotary drill stem (not shown) for rotation thereby, and the lower end of the shank is provided with a coupling means 12 adapted to receive a drill bit 13. An anvil 14 is mounted on the upper surface of the coupling member 12, and a reciprocable hammer body 15 is rotatably mounted on the shank 10 to impact against the anvil 14, all as in my previously described forms. As previously mentioned, the hammer body 15 is provided with an upper collar 22,

Til

and with a lower collar 23 which is adapted to impact against the anvil 14, and the tubular body 21 of the hammer member is provided with longitudinal slots 24 adapted to receive keys 25 of a cam means 40.

The particular cam means I have illustrated in this form of my improved impact drill makes use of a grooved cylindrical cam 41 which is firmly attached to the shank 10 for rotation therewith, While a pair of diametrically opposite projections 42 fit into the groove 43 and act as cam followers. Supporting the projections 42 is a framework or box 44 which encloses the grooved cylindrical cam 41, and which carries keys 25 so that the box rotates with the hammer body 15, but is longitudinally reciprocable with respect to the latter. 'If the groove 43 is given a shape similar to that illustrated, the box 44 will be oscillated when the hammer body 15 is rotated with respect to the shank 10, and this motion of the box may in turn be transmitted to the hammer body by helical springs 45 and 46.

The upper end of the box 44 is provided with a shoulder 47 which extends inwardly to a point just clearing the shank 10, and the lower end of the box is provided with a similar shoulder 48 which is welded or otherwise suitably attached to the box when the device is assembled. The helical spring 45 extends between the lower surface of the upper collar 22 and the upper surface of the shoulder 47, being spaced from the shank 10 so that negligible rubbing therebetween occurs. The helical spring 46 is similarly mounted between the lower surface of the lower shoulder 48 of the box 44, and the upper surface of the lower collar 23 of the hammer body 15. In this way, the entire weight of the hammer body 15 is carried by the box 44, and the weight of the entire resilient assembly is carried by the projections 42 which fit in the groove 43. The strength of the springs 45 and 46 and the weight of the hammer body 15 is correlated so that when the projections 42 are at the lowest points in the groove 43, the lower surface of the collar 23 is adjacent or spaced a very short distance above the anvil 14.

In the operation of this device, the drill assembly is lowered into the hole being drilled and the shank 10 is rotated in the customary drilling fluid. When the shank 10 is rotated, the vanes 20 engage the fluid to provide a drag which overcomes, to a certain degree, the friction existing between the grooved cylindrical cam 41, the cam followers 42 and other points of engagement between the shank and the hammer body 15, so that the latter is retarded in its rotation with respect to the shank 10. The resulting rotation between the cylindrical cam 41 and the cam followers or projections 42 causes the framework or box 44 to be longitudinally oscillated, and this oscillation is transmitted through the helical springs 45 and 46 to the hammer body 15. As the speed of the shank 10 'is increased, the relative speed between it and the hammer body is increased so that eventually the condition of resonance of the resilient system is approached. The amplitude of movement of the hammer body 15 will tend to be the greatest near the point of resonance, and if the lower collar 23 has not previously impacted against the anvil 14, it will do so at this time.

Where the diameter of the well being drilled is relatively small, the diameter of the tubular body 21 will likewise be small and consequently the space available forthe cylindrical cam 41 and the box or framework 44 may be severely restricted. Since the loads imposed upon these members are relatively high, it is generally not practical to reduce their size below a certain minimum value, and consequently I have developed the form of drill shown in Figure 5 for use where space or other requirements render the use of the form shown in Figure 4 impractical. In this form, the cam and box are located outside of the hammer body 15, and are connected by means of a tubular member to a collar axially movable within the hammer body to drive the springs which reciprocate the body.

Considering the construction in somewhat greater detail, the shank 16 is provided with coupling attachments (not shown) at its upper and lower ends for attachment to a drill stem and a drill bit, respectively (not shown), and a hammer body 15a is mounted on the shank for rotational and longitudinal movement with respect thereto. This hammer body 15a is similar to the hammer body 15 used in the previously described forms with the exception that whereas the hammer body 15 may extend upwardly a considerable distance above the upper collar 22, should this be necessary to provide the body with the desired mass, the body 15a has its helical springs and its cam operating members located near its upper end, with the body extending downwardly therefrom a sufficient distance to provide the desired mass. In each case, the hammer body is provided with a lower collar 23 which is adapted to impact against the anvil 14, and it makes no difference in the operation of the device whether the oscillatory force of the helical springs is applied to the body near the upper or lower end of the latter. With these diflerences in mind, it will be seen that the body 15a includes a tubular member 21a having fluid engaging vanes 20 thereon and with an upper collar 50 surrounding theshank 10 but spaced a considerable distance therefrom. An intermediate collar 51 is spaced a considerable distance below the upper collar 50, and under certain circumstances the intermediate collar may be combined with the lower collar 23 (not shown) which strikes against the anvil 14 (not shown).

Axially and rotatably mounted upon the shank 10 within the space between the collars 50 and 51 is a drive collar 52 which is provided with keys or splines 25 to engage corresponding slots 24 in the tubular member 21. The drive collar 52 thus rotates with the hammer body 15a, but is longitudinally movable with respect to the latter and to the shank 10. A drive tube 53, enclosing the shank 10, is rigidly attached to the upper surface of the drive collar 52 and extends upwardly therefrom, through the upper collar 50, to a framework or box 54. Within the latter I mount a grooved cylindrical cam 41 which is rigidly attached to the shank 10 for rotation therewith, and a pair of projections 42 are firmly anchored to the box 54 and fit into the groove 43 of the cam to act as cam followers. To complete this form of my device, I mount a pair of helical springs 45 and 46 between the drive collar 52 and the upper collar 50, and between the intermediate collar 51 and the drive collar 52, respectively.

The operation of this form of my drill is the same as that of the form shown in Figure 4, the only difierence being in that the cam 41 and cam followers 42 are separated from the drive collar 52 instead of being combined as they are in the previously described form. While the structure of the form shown in Figure is slightly more complicated than that of the form shown in Figure 4, the advantages to be secured from the use of the larger box 54 often outweigh the disadvantages of the more complicated structure.

While the forms shown in Figures 4 and 5 provide a different type of resilient support for the hammer member 15, the use of the grooved cylindrical cam 41 provides a more uniform movement for the cam follower means than is provided by the overriding cams of the forms shown in Figures 1 to 3. Consequently, there is no impact delivered to the bit by the cam means themselves, but only by the reciprocation of the hammer body 15. Occasionally it is desirable to have a sharp minor impact delivered to the bit to clear the latter between the major impacts delivered by the hammer body, while retaining the advantages of the particular type of resilient suspension disclosed in Figures 4 and 5. Where the minor impact is to be directed downwardly, as it is where the device shown in Figures 1 and 2 is used, a drill assembly similar to that shown in Figure 6 may be used. It will be noted that the construction of this device is substantially identical with that shown in Figure 4, with the exception that the grooved cylindrical cam 41 and cam followers 42 have been replaced by the overriding cams 16 and 17 as used in the first described forms. The box 40a is modified slightly for attachment to the driven cam 17 instead of to the projections 42, but the other parts and their operation remain unchanged.

When this form of my drill is used in the boring of a well, the rotation ofthe shank 10 tends to rotate the body 15, but the latter is retarded by the action of the drilling fluid on the fluid engaging vanes 20. Consequently, a relative rotation is produced between the body and the shank 10, thereby causing the driven cam 17 to override the driving cam 16, with a minor, downwardly directed impact being delivered to the bit 13 each time the driven cam overrides the driving cam. When the frequency of this overriding approaches the natural frequency of the resiliently supported system, the movement of the box 40a is transmitted by the springs 45 and 46 to the hammer body 15. The latter is thereby oscillated to impact against the anvil 14 and deliver a major impact to the bit 13, the major and minor impacts being alternated so that the bit does not lose its efliciency as a drilling operation proceeds.

Where it is desired to have the minor, cam-actuated impact directed upwardly instead of downwardly to clear the bit, the form shown in Figure 7 may be used which is similar to the form shown in Figure 6 but with the driving and driven cams inverted, similarly to Figure 3. However, if no other method is used to support the hammer body, the latter will move downwardly to rest against the anvil 14, thereby separating the driving and driven cams so that no reciprocation of the hammer will be obtained. To overcome this difiiculty, the hammer is resiliently supported by what might be termed a counterbalancing spring, while a pair of opposed helical springs connect the hammer body to a reciprocating box which is operated by the cam means.

Considering the structure in somewhat greater detail, the upper end of a shank 10 is adapted to be connected to a drill stem (not shown), while the lower end is provided with a coupling means 12 adapted to receive a bit 13, with the upper end of the coupling means being provided with an anvil 14 similar to that previously described. A reciprocable hammer body 15b is mounted on the shank 10, and is provided with fiuid engaging vanes mounted on a tubular body 21b. The lower end of the tubular body 21b is closed by a lower collar 23, and an intermediate collar 22, corresponding to the upper collar 22 of the previously described forms, is spaced a considerable distance above the lower end of the hammer body 15. A box 40b, similar to' the box 4% of the form shown in Figure 6 but inverted, is mounted on the shank 10 between the intermediate collar 22 and the lower collar 23, and is provided with keys adapted to cooperate with longitudinally extending grooves 24 formed in the tubular body 21b. A driving cam 16a is rigidly attached to the shank 10 within the box 40b, and a driven cam 17a is attached to the box and mounted below the driving cam to cooperate with the latter. Helical springs a and 46a are mounted between the box 40b and the intermediate and lower collars 22 and 23 respectively, thereby providing a resilient mounting for the hammer body 15b with respect to the box 40b.

Above the intermediate collar 22 I provide a shoulder or collar which is rigidly attached to the shank 10, and which is adapted to receive and support the lower end or" a helical compression spring 61. The upper end of this spring bears against an upper collar 62 which is rigidly attached to the tubular body 2112, and the strength of the spring 61, its length, and the spacing of 11 the collars 60 and 62 is correlated with the remainder of the assembly so that when the cams 16a and 17a are aligned as shown, the driven cam 17a is urged upwardly against the driving cam 16a.

In the operation of this form of my device, relative rotation between the body 15b and the shank 10 will cause the driven cam 17a to be moved downwardly, thereby forcing the box 40b downward and in turn driving the body 1511 downwardly. When the cam 17a overrides the driving cam 16a, the former is moved upwardly to impact against the driving cam to produce the minor, upwardly directed impact which is transmitted to the bit 13, and the hammer body 15b then starts its upward travel. The cams 16a and 17a then move the box 40b downwardly to drive the hammer body downwardly, and if this is done at the resonant frequency of the resilient system, the lower collar 23 will impact against the anvil 14 to deliver the major, downwardly directed impact which is transmitted to the bit 13.

In all of the different forms of my, invention which have been shown and described herein, it will be noticed that there are cylindrical members which reciprocate with respect to the other members so that an effect somewhat similar to that of a piston within a cylinder is obtained. Since these cylinders quickly become filled with fluid as the drill is lowered into the well, I have provided bleeder holes 65 through these various cylindrical and tubular members so that any tendency to act as a dashpot will be eliminated, and the drilling fluid may move in and out of the cylinders as the latter are reciprocated with respect to other members. These bleed holes 65 have a sufiicient capacity to prevent any entrapment of fluid, and are located in any desired position where they do not interfere with the structural strength or operation of the other parts of the assembly.

These and other modifications may be made without departing from the spirit of my invention, and while I have shown and described several different forms of my invention, I do not wish to be restricted to the particular form or arrangement of parts herein described and shown, except as limited by my claims.

I claim: a

1. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body concentrically mounted on said shank for reciprocation and rotation with respect thereto and provided with retarding means; an anvil rigidly connected to said shank below said hammer body to receive impacts from said hammer body; a driving cam rigidly and concentrically connected to said shank for rotation therewith; a driven cam connected to said hammer body for rotation therewith and concentrically and slidably mounted on said shank for overriding said driving cam and impacting against the latter when said cams rotate with respect to one another, whereby said driven cam is reciprocated with respect to said shank, and said cam impact is transmitted by said shank to said bit; and resilient means coupling said hammer body and said driven cam for transmitting longitudinal movement of said driven cam through said resilient means to said hammer to reciprocate the latter and cause it to impact against said anvil.

2. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body concentrically mounted on said shank for reciprocation and rotation with respect thereto and provided with retarding means; an anvil rigidly connected to said shank below said hammer body to receive impacts from said hammer body; a driving cam concentrically and rigidly connected to said shank for rotation therewith; a driven cam concentrically and slidably mounted above said driving cam, overriding said driving cam and impacting downwardly against the latter when relative rotation occurs between said cams, whereby a reciprocating motion of said driven cam is obtained;

means connecting said driven cam to said hammer body for rotation therewith, and for longitudinal movement with respect to said body, said driven cam producing a downwardly directed impact on said driving cam which is transmitted to said bit-receiving portion by said shank; resilient means connected between said hammer body and said driven cam for transmitting longitudinal movement of said driven cam through said resilient means to said hammer body to reciprocate the latter and cause it to impact downwardly against said anvil; and other resilient means concentrically mounted on said shank within said body opposing the urging of said first resilient means, but permitting reciprocation of said body.

3. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; means mounted on said shank for rotation with respect thereto; a hammer body mounted on said shank for reciprocation with respect thereto; an anvil connected to said shank to receive impacts from said hammer body; a driving cam connected to said shank for rotation therewith; a driven cam mounted below said driving cam, overriding said driving cam and impacting against the latter when relative rotation therebetween occurs, whereby a reciprocating motion of said driven cam is obtained, said driven cam being connected to said first-mentioned means for rotation therewith and longitudinally movable with respect to said body, said driven cam producing an upwardly directed impact on said driv ing cam which is transmitted to said bit-receiving portion by said shank; resilient means connected between said hammer body and said driven cam for transmitting longitudinal movement of said driven cam through said resilient means to said hammer body to reciprocate the latter and cause it to impact downwardly against said an vil; and resilient means extending between said hammer body and said shank to urge said body upwardly and direct said driven cam into operative engagement with said driving cam.

4. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; means mounted on said shank for rotation with respect thereto; a hammer body mounted on said shank for reciprocation with respect thereto; an anvil connected to said shank to receive impacts from said hammer body; cam means connected to said shank and to said firstmentioned means whereby rotation between said shank and said means causes reciprocation of at least a portion of said cam means; resilient means connected between said hammer body and said reciprocable portion of said cam means for transmitting longitudinal movement of said reciprocable portion of said cam means through said resilient means to said hammer body to move the latter and to cause it to impact against said anvil; and a second resilient means opposing the action of said first-'nentioned resilient means, connected between said shank and said hammer body, whereby said body is driven solely by said first resilient means.

5. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; means mounted on said shank for rotation with respect thereto; a hammer body mounted on said shank for reciprocation with respect thereto; an anvil connected to said shank to receive impacts from said hammer body; cam means connected to said shank and to said first-mentioned means whereby rotation between said shank and said means causes reciprocation of at least a portion of said cam means; a first resilient means connected between said hammer body and said reciprocable portion of said cam means; and a second resilient means opposing the urging of said first resilient means, and connected between said hammer body and said reciprocable portion or said cam means, whereby longitudinal movement of said reciprocable portion of said cam means is transmitted through both of said resilient means to said hammer body to move the latter and to cause it to impact against said anvil.

6. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon, and an anvil surface; a tubular hammer body concentrically mounted on sai i shank for longitudinal and rotational movement with respect thereto; means associated with said body for retarding its rotation with respect to said shank; driving cam means within said body rigidly connected to said shank for movement therewith; driven cam means within said body cooperating with said driving cam means and overriding the same, connected to said hammer body for rotation therewith, but longitudinally movable with respect thereto, whereby said driven cam means is reciprocated with respect to said shank when rotated with respect thereto; a first spring connected between said driven cam means and said hammer body and within the latter for transmitting the motion of said cam means to said body; and a second spring connected between said shank and said hammer body and within the latter, opposing the urging of said first spring, whereby said body is resiliently mounted, and reciprocation of said driven cam causes the reciprocation of said hammer body, which impacts downwardly against said anvil.

7. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon, and an anvil surface; a tubular hammer body concentrically mounted on said shank for longitudinal and rotational movement with respect thereto; means on said hammer body for retarding its rotation with respect to said shank; driving cam means concentrically and rigidly connected to said shank for movement therewith; driven cam means concentrically mounted on said shank cooperating with said driving cam means and connected to said hammer body for rotation therewith, but longitudinally movable with respect thereto, whereby said driven cam means is reciprocated with respect to said shank when rotated with respect thereto; a first spring connected between said driven cam means and said hammer body for transmitting the motion of said cam means to said body; and a second spring connected between said driving cam means and said body, opposing the urging of said first springywhereby said body is resiliently supported by said driven cam means, and is caused to reciprocate and impact downwardly against said anvil by the reciprocation of said driven cam means acting through both of said springs.

8. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body mounted substantially concentrically on said shank for longitudinal and rotational movement with respect thereto; means mounted on said body for retarding its rotation with respect to said shank; a driving cam concentric with said shank and rigidly connected to said shank for movement therewith; a driven cam concentric with said shank above said driving cam and cooperating therewith to override said driving cam and impact downwardly against the latter when rotation between said cams occurs; means connecting said driven cam to said hammer body for rotation therewith, and for longitudinal movement with respect thereto; a first spring connected between said driven cam and said hammer body for transmitting the longitudinal motion of said cam to said body; a second spring connected between said driving cam and said body in opposition to said first spring; and an anvil connected to said shank adjacent the lower end of said hammer body to receive a downward impact from said body when the latter is reciprocated.

9. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a hammer body mounted on said shank for longitudinal and rotational movement with respect thereto; means connected to said body for retarding its rotation with respect to said shank; a driving cam rigidly connected to said shank for movement therewith; a driven cam below said driving cam and cooperating therewith to 14 override said driving cam and impact upwardly against the latter when rotation between said cams occurs, said driven cam being connected to said hammer body for rotation therewith, but for longitudinal movement with respect thereto; a spring connected between said driven cam and said hammer body for transmitting the longitudinal motion of said cam to said body, whereby said body is resiliently supported by said cam and longitudinally reciprocated by the movement of said cam; a second spring connected between said hammer body and said shank to urge said body upwardly and thereby maintain said driven cam in operative relationship with said driving cam; and an anvil connected to said shank adjacent the lower end of said hammer body to receive a downward impact from said body when the latter is reciprocated.

10. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body mounted substantially concentrically on said shank for longitudinal and rotational movement with respect thereto; means mounted on said body for retarding its rotation with respect to said shank; a driving cam located within said body, rigidly attached to said shank for rotation therewith; a driven cam located within said body above said driving cam to cooperate with the latter, said driven cam overriding said driving cam and impacting downwardly against the latter when rotation therebetween occurs; means connecting said driven cam to said hammer body for longitudinal movement with respect thereto, while preventing relative rotation therebetween; a first spring extending between said driven cam and said body for transmitting the longitudinal movement of said cam to said body to reciprocate the latter; a second spring extending between said driving cam and said body and opposing the urging of said first spring; and an anvil attached to said shank adjacent the lower end of said hammer body for receiving a downward impact from the latter when said body is reciprocated.

11. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body mounted substantially concentrically on said shank for longitudinal and rotational movement with respect thereto; means mounted on said body for retarding its rotation with respect to said shank; a driving cam located within said body, rigidly attached to said shank for rotationtherewith; a driven cam located within said body below said driving cam to cooperate with the latter, said driven cam overriding said driving cam and impacting upwardly against the latter when rotation therebetween occurs; means connecting said driven cam to said hammer body for longitudinal movement with respect thereto, while preventing relative rotation therebetween; a first spring extending between said driven cam and said body for transmitting the longitudinal movement of said cam to said body to reciprocate the latter; a second spring extending between said driving cam and said body and opposing the urging of said first spring; and an anvil'attached to said shank adjacent the lower end of said hammer body for receiving a downward impact from the latter when said body is reciprocated.

12. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body mounted substantially concentrically on said shank for longitudinal and rotational movement with' respect thereto; means mounted on said body for retarding its rotation with respect to said shank; a box member mounted adjacent said body for rotation therewith but longitudinally movable with respect thereto, said box member being mounted for rotational and longitudinal movement with respect to said shank; a grooved cylindrical cam and follower means connecting said box member to said shank whereby said box member is longitudinally reciprocable when relative rotation between said box member and said shank occurs; a first spring extending upwardly from said box member 15 to said hammer body; a second spring extending downwardly from said box member to said body, whereby said body is resiliently mounted and is reciprocated upon said shank by the longitudinal movement of said box member; and an anvil attached to said shank adjacent the lower end of said hammer body to receive an impact therefrom when said body is longitudinally reciprocated.

13. An impact drill of the class described which includes: a rotatable shank having a bit-receiving portion thereon; a tubular hammer body mounted substantially concentrically on said shank for longitudinal and rotational movement with respect thereto; means mounted on said body for retarding its rotation with respect to said shank; a box member mounted adjacent said body for rotation therewith but longitudinally movable with respect thereto, said box member being mounted for rotational and longitudinal movement with respect to said shank; a pair of overriding cam means connecting said box member to said shank and comprising a driving cam rigidly connected to said shank and a cooperating driven cam rigidly attached to said box member whereby said box member is longitudinally reciprocated when relative rotation between said box member and said shank occurs; a first spring extending upwardly from said box member to said hammer body; a second spring extending downwardly from said box member to said body, whereby said body is resiliently mounted and is reciprocated upon said shank by the longitudinal movement of said box member; and an anvil attached to said shank adjacent the lower end of said hammer body to receive an impact therefrom when said body is longitudinally reciprocated.

14. An impact drill of the class described which includes: a shank adapted to be attached to and rotated by a drill stem and having an anvil rigid therewith; a tubular hammer body mounted substantially concentrically on said shank above said anvil for axial and rotational movement with respect to said shank; means mountedon said body for retarding its rotation with respect to said shank; driving cam means rigidly attached to said shank; driven cam means slidably mounted above said driving cam on said shank for axial and rotational movement with respect to said shank and said driving cam means; means connecting said driven cam means to said hammer body for rotation therewith but permitting axial movement with respect thereto; spring means between said driven cam means and said hammer body for transmitting axial motion from said driven cam means to said hammer body to reciprocate said body and cause the same to deliver periodic downward impacts to said anvil;

and spring means between said driving cam and said body.

15. An impact drill of the class described which includes: a shank adapted to be attached to and rotated by a drill stem and having an anvil rigid therewith; a tubular hammer body concentrically mounted on said shank above said anvil for axial and rotational movement with respect to said shank; retarding means on said body; driving cam means rigidly attached to said shank; driven cam means mounted on said shank within said body for axial and rotational movement with respect to said shank and said driving cam means; means connecting said driven cam means to said hammer body for rotation therewith but permitting axial movement with respect thereto; first spring means supporting said hammer body above said anvil and providing resilient connection between said driven cam means and said hammer body to reciprocate the latter upon reciprocation of said driven cam means; and second spring means within said body acting in opposition to said first spring means to establish resonance.

16. An impact drill of the class described which includes: a shank adapted to be attached to and rotated by a drill stem and having an anvil rigid therewith; a tubular hammer body concentrically mounted on said shank above said anvil for axial and rotational movementwith respect to said shank; driving cam means rigidly attached to said shank; driven cam means mounted on said shank above said driving cam means for axial and rotational movement with respect to said shank and said driving cam means; means connecting said driven cam means to said hammer body for rotation therewith but permitting axial movement with respect thereto; and resilient means for supporting said tubular hammer body above said anvil including upper and lower springs mounted on said shank within said body, at least one of said springs being between said body and said driven cam means to resiliently transmit to said body axial motion of said driven cam means to thereby reciprocate said body and cause it to deliver periodic downward impacts to said anvil, and the other of said springs being between said body and said driving cam means in opposition to said first spring means.

References Cited in the file of this patent UNITED STATES PATENTS 471,580 Webber Mar. 29, 1892 1,745,351 Bishop Feb. 4, 1930 1,899,438 Grant Feb. 28, 1933 2,146,454 Sutlift' Feb. 7, 1939 2,228,482 Prebensen Jan. 14, 1941 2,287,157 Wolfi June 23, 1942 2,371,248 McNamara Mar. 13, 1945 2,425,012 Snyder Aug. 5, 1947 

